R5#sh ip ospf int lo1
Loopback1 is up, line protocol is up
Internet Address 10.10.0.1/24, Area 10
Process ID 1, Router ID 10.10.3.1, Network Type LOOPBACK, Cost: 1
Loopback interface is treated as a stub Host
OSPF treats loopback and virtual links as stub host with a mask of /32.
The behaviour can be changed by inserting a port-base command : ip ospf network point-to-point
R5(config)#int lo1
R5(config-if)#ip ospf network point-to-point
R5#sh ip ospf int lo1
Loopback1 is up, line protocol is up
Internet Address 10.10.0.1/24, Area 10
Process ID 1, Router ID 10.10.3.1, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Index 2/2, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
cyruslab 